1. Technical Field
The present invention relates to an image forming device, such as a copier or a printer or the like, which uses an electrophotographic method. In particular, the present invention relates to an image forming device having a contact-charging-type charging roller which, while rotating while contacting an image holding member which is driven to rotate, charges the surface of the image holding member, and a cleaning roller which cleans the charging roller.
2. Related Art
In recent years, roller chargers (BCR), which are disposed so as to contact or so as to be adjacent to an image holding member, have been used as the charging device of an image forming device such as a copier or a printer or the like which uses an electrophotographic method, instead of a conventional non-contact-type charger such as a scorotron or the like, in order to suppress ozone discharge, make the device more compact, reduce high voltage power source costs, and the like.
In such a contact-charging-method charging device, because the charging roller is always contacting the image holding member, there is the problem that it is easy for contamination to arise, due to foreign matter adhering to the surface of the charging roller. At the downstream side of the transfer process, the surface of the image holding member, at which the image forming operation is repeatedly carried out, is subject to a cleaning process which removes foreign matter such as residual toner and the like after the transfer. Thereafter, the surface of the image holding member enters into the area of the charging process. However, even after being subjected to the cleaning process, minute particles which are smaller than the toner, such as portions of the toner particles or external additives of the toner or the like, remain on the image holding member without being cleaned, and adhere to the surface of the charging roller. The foreign matter adhering to the surface of the charging roller causes non-uniformity in the surface resistance value of the charging roller, and abnormal discharging or unstable discharging occurs, and the uniformity of charging deteriorates.